The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Clutch units may be used, for example, in transfer cases of motor vehicles with which the torque generated by a drive unit is transferred to the individual vehicle wheels as required. For example, in motor vehicles with temporarily connectable all-wheel drive, some of the drive torque is fixedly transferred to the primary drive wheels, whereas a second portion of the drive torque is transferred as required, for example in dependence on corresponding driving dynamic parameters underlying the respective driving situation, to the two other vehicle wheels (i.e., to the secondary drive wheels). Furthermore, such clutch units may also be used for the transfer of the torque between the left hand vehicle wheels and the right hand vehicle wheels, or for any other transfer of a torque.
So-called driving dynamic parameters are usually determined and/or evaluated by the main control unit for the generation of a corresponding setting signal for the actuator. In this connection, it can, for example, be a question of parameters such as vehicle speed, vehicle acceleration, tire slip, speed of the gas pedal actuation, drive torque, steering angle, wheel speed, yaw rate or yaw angle speed, or other parameters influencing the driving dynamics.
A respective desired value for the then current torque to be transmitted is determined by the main control unit based on these first parameters. This desired value is transmitted to the additional control unit, which generates a setting signal corresponding to the desired value for the actuator based on the desired value. The setting signal may, for example, be an angle of rotation of the actuator corresponding to the respective torque to be set or, for example, a corresponding pressure value.
To reduce the number of the setting movements of the actuator occurring on each torque demand, and thus to reduce the thermal strain of the actuator, it is known that a tolerance band for the torque to be set is stored within the additional control unit and a setting procedure of the actuator is only triggered on a minimum change of the desired value (i.e., when the desired value departs from the tolerance band). From the vehicle aspect, a degradation of the torque precision of the system may thereby result by which, however, the driving behavior is not negatively influenced in many driving situations. There are, however, driving situations where very high precision is required for the setting of the torque to be transmitted. Furthermore, the taking into account of a tolerance band within the additional control unit is not flexible since, for example, dynamic driving parameters or dynamic influences in the region of the clutch unit or of the actuator cannot be taken into account.